SYRACUSE, N.Y. -- Several public power agencies and consumer advocates expressed disappointment this week at the outcome of a 14-month federal investigation which found that New York energy traders committed neither fraud nor market manipulation in a 2008 trading scheme that cost consumers perhaps $95 million in unnecessary charges.

The Federal Energy Regulatory Commission's decision, announced last week, means that no refunds will be sought from nine energy trading companies that engaged in certain interstate power sales that were permitted last year but have since been prohibited.

To avoid high transmission costs on congested New York power lines, the energy marketers scheduled power sales that -- on paper, anyway -- sent power on circuitous paths around Lake Erie and through the Midwest to reach Pennsylvania.

In 80 percent of the cases, the actual electricity ignored the scheduled transmission path and flowed through New York anyway, forcing grid operators to take expensive steps to relieve the resulting congestion.

The New York Independent System Operator, which operates the state power grid, estimated that the transactions added $95 million in extra costs that were ultimately borne by the state's electric consumers. Some wholesale energy traders estimated the extra cost at $250 million or more.

Anthony Modafferi, executive director of the Municipal Electric Utilities Association, which represents 40 municipal power companies, said he had hoped the small utilities could get back some of their costs, which were "in the millions." Transmission costs were unusually high during the first half of 2008, when the unusual power trades were going on. "After having waited for about a year and a half now, it was disappointing to hear that," Modafferi said.

FERC concluded that the trading companies used the circuitous transmission routes to enhance profits, but said there was no rule in place at the time prohibiting the tactic. And although the transactions contributed to unstable power flows that increased system costs, it would have been difficult for the companies to predict those effects, investigators said. FERC approved the NYISO's request to prohibit the transactions in July 2008.

Gerald Norlander, executive director of the Public Utility Law Project, said FERC's ruling fixes the immediate problem but does little to discourage energy companies from looking for similar market anomalies to exploit. "The invitation is, find another flaw and go for it. That's the lesson here," Norlander said.